<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <title>Title</title>
    <style>
        h1, #box {
            margin: 0px auto;
            text-align: center;
        }
        #box{
            position: relative;
            width: 400px;
            height: 400px;
        }
        dt img {
            width: 320px;
        }

        dl {
            margin: 0px auto;
            border: 1px solid #ccc;
            width: 340px;
        }

        dd {
            margin-left: 0px;
            font-size: small;
            color: #444;
            height: 20px;
            background: #ccc;
        }

        .hot_bar{
            z-index: 0;
            position: absolute;
            top: 0px;
            right:24px;
            width: 120px;
            transform:rotate(40deg);
            opacity: 0.8;
        }
    </style>
</head>
<body>
<h1>z-index案例</h1>
<hr>
<div id="box">
    <dl>
        <dt><img src="https://img.simoniu.com/小米10.jpeg"/></dt>
        <dd>小米10(8+256版) &nbsp;&nbsp;&nbsp;2999￥</dd>
    </dl>
    <img class="hot_bar" src="https://img.simoniu.com/hot_sale.png"/>
</div>
</body>
</html>